Melatonin and protection from genetic damage in blood and bone marrow: Whole-body irradiation studies in mice

The objective of this study was to examine the potential radioprotective pr operties of pharmacological doses of melatonin in whole-body irradiated mic e. CD2-F1 male mice were treated with melatonin, a secretory product of the pineal gland, and then whole-body irradiated with an acute dose (150 cGy) of Cs-137 gamma rays. Peripheral blood and bone marrow cells were examined for genetic damage, which was determined by comparing the incidence of micr onuclei (MN) in both melatonin pre-treated and non-treated irradiated anima ls (and control mice). The percentages of polychromatic erythrocytes (PCEs) in unirradiated mice ranged between 3.1 +/- 0.23 and 3.2 +/- 0.19 in the p eripheral blood and between 51.0 +/- 2.03 and 52.8 +/- 2.00 in the bone mar row. Whole-body irradiation resulted in a significant decrease in the perce ntages of PCEs in the peripheral blood and bone marrow cells. In both tissu es, irradiated mice that were pre-treated with melatonin (5 or 10 mg/kg) ex hibited a dose-dependent increase in the observed incidence of PCEs relativ e to the expected incidence. The incidence of MN in unirradiated mice range d between 4.2 +/- 0.92 and 4.6 +/- 0.97 in the peripheral blood and between 5.0 +/- 1.05 and 5.5 +/- 1.08 in the bone marrow. Whole-body irradiation r esulted in a significant increase in the incidence of MN in both tissues. I n both tissues, irradiated mice that were pre-treated with melatonin exhibi ted a significant and dose-dependent reduction in the observed incidence of MN (relative to the expected incidence). Under the experimental conditions tested, the data indicate that melatonin has the ability to protect the ge netic material of hematopoietic cells of mice from the damaging effects of acute whole-body irradiation.